Abstract

We discuss some effects related to particle coherent orbits in the acceleration region and in the wind. (1) In the distant wind, when collisions are negligible, the temperature of escaping electrons follows adiabatic anisotropic (CGL) relations, whereas those reflected by the electrostatic and/or mirror forces behave as an adiabatic isotropic fluid; hence, contrary to a widespread view, electrons do not follow a single adiabatic law in absence of collisions. (2) In the corona, if one superimposes a minute hot maxwellian tail to a maxwellian velocity distribution, the relative importance of the tail increases rapidly with height; this is fundamentally different from a Kappa distribution, whose non maxwellian character remains constant with height. Suprathermal electrons also produce a large heat flux because many of them escape from the electric potential. (3) Fluid models, exospheric models, and a numerical simulation including particle orbits and collisions agree on finding that when an accelerated transonic wind is produced, the potential energy of protons has a maximum, so that some protons can be reflected; the production of a transonic wind also requires the trapped electron
orbits to be populated, which requires some collisions. Finally, since particles on different kinds of orbits behave very differently, fluid models should not consider each particle species as a single fluid; each species should be modelled instead as a superposition of several fluids having different transport properties.